e+e−e^{+}e^{-} pairs from a nuclear transition signaling an elusive light neutral boson

Electron-positron pairs have been observed in the 10.95-MeV $0^-\to0^+$ decay in $^{16}$O. The branching ratio of the e$^+$e$^-$ pairs compared to the 3.84-MeV $0^-\to2^+$ $\gamma$ decay of the level is deduced to be $20(5)\times10^{-5}$. This magnetic monopole (M0) transition cannot proceed by $\gamma$-ray decay and is, to first order, forbidden for internal pair creation. However, the transition may also proceed by the emission of a light neutral $0^{-}$ or $1^{+}$ boson. Indeed, we do observe a sharp peak in the $e^{+}e^{-}$ angular correlation with all the characteristics belonging to the intermediate emission of such a boson with an invariant mass of 8.5(5) MeV/c$^2$. It may play a role in the current quest for light dark matter in the universe.Comment: 6 page

A Large Outbreak of Legionnaires’ Disease at a Flower Show, the Netherlands, 1999

In 1999, an outbreak of Legionnaires’ disease affected many visitors to a flower show in the Netherlands. To identify the source of the outbreak, we performed an environmental investigation, as well as a case-control study among visitors and a serologic cohort study among exhibitors to measure exposure to possible sources. Of 77,061 visitors, 188 became ill (133 confirmed and 55 probable cases), for an attack rate of 0.23% for visitors and 0.61% for exhibitors. Two whirlpool spas in halls 3 and 4 of the exhibition and a sprinkler in hall 8 were culture positive for Legionella pneumophila. One of three genotypes found in both whirlpool spas was identical to the isolates from 28 of 29 culture-positive patients. Persons who paused at the whirlpool spa in hall 3 were at increased risk for becoming ill. This study illustrates that whirlpool spas may be an important health hazard if disinfection fails

Coherent bremsstrahlung, boherent pair production, birefringence and polarimetry in the 20-170 GeV energy range using aligned crystals

The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20-170 GeV. The experimental arrangement allowed for measurements of single photon properties of these phenomena including their polarization dependences. This is significant as the theoretical description of CB and CPP is an area of active theoretical debate and development. With the theoretical approach used in this paper both the measured cross sections and polarization observables are predicted very well. This indicates a proper understanding of CB and CPP up to energies of 170 GeV. Birefringence in CPP on aligned crystals is applied to determine the polarization parameters in our measurements. New technologies for high energy photon beam optics including phase plates and polarimeters for linear and circular polarization are demonstrated in this experiment. Coherent bremsstrahlung for the strings-on-strings (SOS) orientation yields a larger enhancement for hard photons than CB for the channeling orientations of the crystal. Our measurements and our calculations indicate low photon polarizations for the high energy SOS photons.Comment: 23 pages, 27 figures, 2 tables, REVTeX4 two column

Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)

The muon-proton and muon-deuteron inclusive deep inelastic scattering cross sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 < 75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results are based on the full data set collected by the New Muon Collaboration, including the data taken with a small angle trigger. The extracted values of the structure functions F2p and F2d are in good agreement with those from other experiments. The data cover a sufficient range of y to allow the determination of the ratio of the longitudinally to transversely polarised virtual photon absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The values of R are compatible with a perturbative QCD prediction; they agree with earlier measurements and extend to smaller x.Comment: In this replacement the erroneously quoted R values in tables 3-6 for x>0.12, and R1990 values in tables 5-6 for all x, have been corrected, and the cross sections in tables 3-4 have been adapted. Everything else, including the structure functions F2, remained unchanged. 22 pages, LateX, including figures, with two .sty files, and three separate f2tab.tex files for the F2-tables. Accepted for publication in Nucl.Phys.B 199

Nationwide Association of Surgical Performance of Minimally Invasive Esophagectomy With Patient Outcomes

IMPORTANCE: Suboptimal surgical performance is hypothesized to be associated with less favorable patient outcomes in minimally invasive esophagectomy (MIE). Establishing this association may lead to programs that promote better surgical performance of MIE and improve patient outcomes.OBJECTIVE: To investigate associations between surgical performance and postoperative outcomes after MIE.DESIGN, SETTING, AND PARTICIPANTS: In this nationwide cohort study of 15 Dutch hospitals that perform more than 20 MIEs per year, 7 masked expert MIE surgeons assessed surgical performance using videos and a previously developed and validated competency assessment tool (CAT). Each hospital submitted 2 representative videos of MIEs performed between November 4, 2021, and September 13, 2022. Patients registered in the Dutch Upper Gastrointestinal Cancer Audit between January 1, 2020, and December 31, 2021, were included to examine patient outcomes.EXPOSURE: Hospitals were divided into quartiles based on their MIE-CAT performance score. Outcomes were compared between highest (top 25%) and lowest (bottom 25%) performing quartiles. Transthoracic MIE with gastric tube reconstruction.MAIN OUTCOME AND MEASURE: The primary outcome was severe postoperative complications (Clavien-Dindo ≥3) within 30 days after surgery. Multilevel logistic regression, with clustering of patients within hospitals, was used to analyze associations between performance and outcomes.RESULTS:In total, 30 videos and 970 patients (mean [SD] age, 66.6 [9.1] years; 719 men [74.1%]) were included. The mean (SD) MIE-CAT score was 113.6 (5.5) in the highest performance quartile vs 94.1 (5.9) in the lowest. Severe postoperative complications occurred in 18.7% (41 of 219) of patients in the highest performance quartile vs 39.2% (40 of 102) in the lowest (risk ratio [RR], 0.50; 95% CI, 0.24-0.99). The highest vs the lowest performance quartile showed lower rates of conversions (1.8% vs 8.9%; RR, 0.21; 95% CI, 0.21-0.21), intraoperative complications (2.7% vs 7.8%; RR, 0.21; 95% CI, 0.04-0.94), and overall postoperative complications (46.1% vs 65.7%; RR, 0.54; 95% CI, 0.24-0.96). The R0 resection rate (96.8% vs 94.2%; RR, 1.03; 95% CI, 0.97-1.05) and lymph node yield (mean [SD], 38.9 [14.7] vs 26.2 [9.0]; RR, 3.20; 95% CI, 0.27-3.21) increased with oncologic-specific performance (eg, hiatus dissection, lymph node dissection). In addition, a high anastomotic phase score was associated with a lower anastomotic leakage rate (4.6% vs 17.7%; RR, 0.14; 95% CI, 0.06-0.31).CONCLUSIONS AND RELEVANCE: These findings suggest that better surgical performance is associated with fewer perioperative complications for patients with esophageal cancer on a national level. If surgical performance of MIE can be improved with MIE-CAT implementation, substantially better patient outcomes may be achievable.</p

Candida albicans repetitive elements display epigenetic diversity and plasticity

Transcriptionally silent heterochromatin is associated with repetitive DNA. It is poorly understood whether and how heterochromatin differs between different organisms and whether its structure can be remodelled in response to environmental signals. Here, we address this question by analysing the chromatin state associated with DNA repeats in the human fungal pathogen Candida albicans. Our analyses indicate that, contrary to model systems, each type of repetitive element is assembled into a distinct chromatin state. Classical Sir2-dependent hypoacetylated and hypomethylated chromatin is associated with the rDNA locus while telomeric regions are assembled into a weak heterochromatin that is only mildly hypoacetylated and hypomethylated. Major Repeat Sequences, a class of tandem repeats, are assembled into an intermediate chromatin state bearing features of both euchromatin and heterochromatin. Marker gene silencing assays and genome-wide RNA sequencing reveals that C. albicans heterochromatin represses expression of repeat-associated coding and non-coding RNAs. We find that telomeric heterochromatin is dynamic and remodelled upon an environmental change. Weak heterochromatin is associated with telomeres at 30?°C, while robust heterochromatin is assembled over these regions at 39?°C, a temperature mimicking moderate fever in the host. Thus in C. albicans, differential chromatin states controls gene expression and epigenetic plasticity is linked to adaptation

Testing "microscopic" theories of glass-forming liquids

We assess the validity of "microscopic" approaches of glass-forming liquids based on the sole k nowledge of the static pair density correlations. To do so we apply them to a benchmark provided by two liquid models that share very similar static pair density correlation functions while disp laying distinct temperature evolutions of their relaxation times. We find that the approaches are unsuccessful in describing the difference in the dynamical behavior of the two models. Our study is not exhausti ve, and we have not tested the effect of adding corrections by including for instance three-body density correlations. Yet, our results appear strong enough to challenge the claim that the slowd own of relaxation in glass-forming liquids, for which it is well established that the changes of the static structure factor with temperature are small, can be explained by "microscopic" appr oaches only requiring the static pair density correlations as nontrivial input.Comment: 10 pages, 7 figs; Accepted to EPJE Special Issue on The Physics of Glasses. Arxiv version contains an addendum to the appendix which does not appear in published versio

Performance of the LHCb vertex locator

The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 μm is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 μm for translations in the plane transverse to the beam. A primary vertex resolution of 13 μm in the transverse plane and 71 μm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 μm is achieved for particles with transverse momentum greater than 1 GeV/c